Conventional steering arrangements include a steering motor, having a steering motor angle sensor, a steering member, having a steering member angle sensor, and a compensation device, which controls a control system in dependence of signals from the steering motor angle sensor and the steering member angle sensor. A method and a steering arrangement of this kind are known from U.S. Pat. No. 5,549,173.
Steering handwheels with buttons are also available, whose “real” position is very important, in order that the operator can always reach the buttons correctly. The buttons are operating elements, with which certain functions can be triggered.
Of course, the same also applies for other vehicles, for example boats or aircraft, in which the steering member is in the form of a steering handwheel or a joystick. In all these cases, it is desired to give the operator or the driver information about the position of the steered element of the vehicle. This also applies, when the steering member, for example the steering handwheel, must perform more than one rotation to achieve complete utilisation of the angle area of the steering motor. In this case, the neutral position will be passed more than once. In one position of the steering handwheel, however, the neutral position should correspond to the neutral position of the steered wheels.
In such steering systems, errors occur, which may cause that the neutral position of the steering member no longer corresponds with the straightforward position of the steered wheel. In systems, which comprise a hydraulic steering, such errors may be caused by the fact that hydraulic components have a leakage. Other reasons for deviations in the conformance are wear phenomenon, which, for example, occur in knuckle joints.
Therefore, U.S. Pat. No. 5,549,173, mentioned in the introduction discloses a compensation of deviations occurring between the position of the steering member and the position of the steering motor. For this purpose, data are stored in a table, which can change the active connection between the signal of the steering member and the effect of the steering motor, depending on differences between the steering motor angle and the steering member angle. For example, the steering motor can be moved in the normal direction. However, it can also be stopped, or even moved in the opposite direction.
From older publications, for example DE 40 42 153 C2 or DE 40 42 151 C2, it is known, with a hydraulic steering to either increase or reduce the flow of the hydraulic fluid for the compensation of such a steering angle error, to re-establish a concordance between the steering motor angle and the steering member angle.
In the known cases, however, it is only possible to compensate the steering angle error, that is, the deviation between the steering member angle and the steering motor angle at certain spots. Faults caused by leakages or slip, which occur at other spots, for example between a steering handwheel and a steering column or in a connection to a steering unit cannot be compensated.
It is therefore a primary objective of this invention to improve the steering of a vehicle.